1. Metabolic Processes Part 3 Interconnections of Metabolic Pathways and Anaerobic Respiration

2. Interconnections of Metabolic Pathways We can use other foods for energy (carbs other than glucose, proteins, fats) Most carbohydrates are broken down into glucose first, then enter the pathway much like glucose would. Proteins: amino group is taken off and the rest of the amino acids will enter the Pathway at various parts Fats: glycerol is converted into glyceraldehyde-3- phosphate (which is in glycolysis) and the fatty acids are transported into the mitochondria and carbon atoms are removed 2 at a time to create acetyl groups and enter at the Krebs Cycle. We can use other foods for energy (carbs other than glucose, proteins, fats) Most carbohydrates are broken down into glucose first, then enter the pathway much like glucose would. Proteins: amino group is taken off and the rest of the amino acids will enter the Pathway at various parts Fats: glycerol is converted into glyceraldehyde-3- phosphate (which is in glycolysis) and the fatty acids are transported into the mitochondria and carbon atoms are removed 2 at a time to create acetyl groups and enter at the Krebs Cycle.

4. Anaerobic Respiration Some organisms do not use oxygen as the final electron acceptor. Instead they may use sulfate, nitrate or carbon dioxide. Some other organisms such as methanogens will have a different metabolic pathway (4H2 + CO2 -> CH4 + 2H2O) Some organisms do not use oxygen as the final electron acceptor. Instead they may use sulfate, nitrate or carbon dioxide. Some other organisms such as methanogens will have a different metabolic pathway (4H2 + CO2 -> CH4 + 2H2O)

5. Fermentation Some single-celled organisms use only glycolysis to obtain energy Two common fermentation pathways: Lactate Fermentation: pyruvate generated by glycolysis reacts with NADH to reoxidize NAD+ and pyruvate is converted to lactate. In bacteria, this lactate is secreted into the surroundings making an acidic environment In animals, this process can happen when we don’t have enough oxygen. The excess lactate will eventually be converted back to pyruvate and oxidized. Some single-celled organisms use only glycolysis to obtain energy Two common fermentation pathways: Lactate Fermentation: pyruvate generated by glycolysis reacts with NADH to reoxidize NAD+ and pyruvate is converted to lactate. In bacteria, this lactate is secreted into the surroundings making an acidic environment In animals, this process can happen when we don’t have enough oxygen. The excess lactate will eventually be converted back to pyruvate and oxidized.

6. Fermentation Continued… Ethanol Fermentation: Yeast and some bacteria convert pyruvate into ethanol and CO2. Pyruvate changes into acetaldehyde by cleaving off a CO2 which then changes into ethanol. Used to manufacture baked goods and alcoholic beverages. In ethanol fermentation, ethanol is a byproduct, but it still has a lot of energy in the molecule. Lately, we have been using ethanol in our gasoline (up to 10%) as a fuel. Ethanol Fermentation: Yeast and some bacteria convert pyruvate into ethanol and CO2. Pyruvate changes into acetaldehyde by cleaving off a CO2 which then changes into ethanol. Used to manufacture baked goods and alcoholic beverages. In ethanol fermentation, ethanol is a byproduct, but it still has a lot of energy in the molecule. Lately, we have been using ethanol in our gasoline (up to 10%) as a fuel.